Storage device management techniques for a remote storage digital video recorder that handles multiple bitrate content

ABSTRACT

A remote storage digital video recorder (RS-DVR) system is disclosed. The RS-DVR system includes a network interface to communicate data between the RS-DVR system and a subscriber system via a network, a file system module coupled to the network interface, an ingest agent coupled to the file system module to receive encoded media segments that represent media content files encoded at a plurality of different bitrates; and a storage architecture coupled to the file system to store the encoded media segments, resulting in stored media segments. The RS-DVR carries out a number of functions and operations to service multiple subscribers and associated subscriber systems, such as various storage device management operations, file structure techniques, assignment of recorded media to subscribers, file system indexing, and supporting shared and per-subscriber content rights.

CROSS-REFERENCE TO RELATED APPLICATION

This Application claims priority to U.S. Provisional Application Ser.No. 61/567,513, filed Dec. 6, 2011.

TECHNICAL FIELD

Embodiments of the subject matter described herein relate generally to aremote storage digital video recorder (RS-DVR) system and relatedoperating methods.

BACKGROUND

A digital video recorder (DVR) can store a digital representation of avideo program for subsequent playback. Traditionally, DVRs have beenpurchased or leased by customers for personal use at the customerpremises. For example, a cable or satellite television subscriber mighthave a DVR at the home to accommodate recording of broadcast programsdelivered by the cable or satellite television system. A DVR may beprovided as a standalone unit or it may be integrated into anothercomponent, such as a set top box for a cable or satellite televisionsystem.

An RS-DVR system can be utilized as an alternative to traditional DVRsthat must be deployed and located at the customer site. An RS-DVR systemcan remotely provide content recording and playback capabilities to anynumber of subscribers and end users (similar to a video-on-demandsystem). In practice, therefore, an RS-DVR system can communicate with aplurality of different subscriber systems via a data communicationnetwork.

An RS-DVR system should be able to deliver digital media content in areliable manner over managed or unmanaged networks under various degreesof congestion. To facilitate this, it would be desirable to have anRS-DVR system that is capable of supporting multiple bitrate digitalmedia content. Furthermore, other desirable features and characteristicswill become apparent from the subsequent detailed description and theappended claims, taken in conjunction with the accompanying drawings andthe foregoing technical field and background.

BRIEF SUMMARY

An embodiment of an RS-DVR system is provided here. The RS-DVR systemincludes a network interface to communicate data between the RS-DVRsystem and a subscriber system via a network, a file system modulecoupled to the network interface, an ingest agent coupled to the filesystem module to receive encoded media segments that represent mediacontent files encoded at a plurality of different bitrates, and astorage architecture coupled to the file system to store the encodedmedia segments, resulting in stored media segments. The networkinterface, the file system module, and the storage architecturecooperate to provide the stored media segments to the subscriber systemfor presentation using at least one of the plurality of differentbitrates.

Also provided is an embodiment of a method of operating an RS-DVR systemthat supports a subscriber system via data communication over a network.The method involves receiving, at the RS-DVR system, encoded mediasegments that represent a media content file encoded at a plurality ofdifferent bitrates, along with an instruction to record the mediacontent file on behalf of a subscriber. In response to receiving theinstruction, the method stores the encoded media segments in a storagearchitecture of the RS-DVR system, resulting in stored media segments.

Also provided is an embodiment of a method of operating an RS-DVR systemthat supports subscriber systems via data communication over a network.The method involves receiving, at the RS-DVR system, encoded mediasegments that represent a media content file encoded at a plurality ofdifferent bitrates, wherein the encoded media segments include arespective set of encoded media segments corresponding to each of theplurality of different bitrates. The method also receives, at the RS-DVRsystem, a first instruction to record the media content file on behalfof a first subscriber. In response to receiving the first instruction,the method stores a first instantiation of the encoded media segments ina storage architecture of the RS-DVR system, resulting in a first groupof stored media segments. The method continues by receiving, at theRS-DVR system, a second instruction to record the media content file onbehalf of a second subscriber. In response to receiving the secondinstruction, the method stores a second instantiation of the encodedmedia segments in a storage architecture of the RS-DVR system, resultingin a second group of stored media segments.

Another embodiment of an RS-DVR system is also provided. The RS-DVRsystem includes a network interface to communicate data between theRS-DVR system and a subscriber system via a network, a file systemmodule coupled to the network interface, and an ingest agent coupled tothe file system module to receive encoded media segments that representa media content file encoded at a plurality of different bitrates. Theencoded media segments include a respective set of encoded mediasegments corresponding to each of the plurality of different bitrates,and each of the encoded media segments has a time range relative to themedia content file. The RS-DVR system also includes a plurality ofmemory storage devices coupled to the file system to store the encodedmedia segments in accordance with a distribution scheme influenced bythe plurality of different bitrates and time ranges of the encoded mediasegments.

Also provided is a related method of operating an RS-DVR system thatsupports a subscriber system via data communication over a network. Themethod involves receiving, at the RS-DVR system, encoded media segmentsthat represent a media content file encoded at a plurality of differentbitrates. The encoded media segments include a respective set of encodedmedia segments corresponding to each of the plurality of differentbitrates, and each of the encoded media segments has a time rangerelative to the media content file. The method continues by storing theencoded media segments in a plurality of memory storage devices of theRS-DVR system, wherein the storing is performed in accordance with adistribution scheme to ensure that encoded media segments havingdifferent bitrates and overlapping time ranges are not stored on acommon one of the plurality of memory storage devices. After storing theencoded media segments, the method receives, at the RS-DVR system, arequest for playback of the media content file, the request identifyinga requested bitrate for the media content file. The method continues bydetermining, at the RS-DVR system, whether the plurality of memorystorage devices can maintain real-time delivery of encoded mediasegments having the requested bitrate. When the RS-DVR system determinesthat one of the plurality of memory storage devices cannot maintainreal-time delivery of encoded media segments having the requestedbitrate, generating, at the RS-DVR system, a message intended for thesubscriber system, wherein the message instructs the subscriber systemto request a different bitrate for the media content file.

Also presented here is an embodiment of a method of operating an RS-DVRsystem that supports at least one subscriber system via datacommunication over a network. The method begins by receiving, at theRS-DVR system, a first set of encoded media segments that represent amedia content file encoded at a first bitrate, and a second set ofencoded media segments that represent the media content file encoded ata second bitrate. Each encoded media segment in the first set of encodedmedia segments corresponds to a respective partial period of playbacktime of the media content file, and each encoded media segment in thesecond set of encoded media segments corresponds to a respective partialperiod of playback time of the media content file. The method proceedsby receiving, at the RS-DVR system, an instruction to record the mediacontent file on behalf of a subscriber. In response to receiving theinstruction, the method stores the first set of encoded media segmentsand the second set of encoded media segments in a plurality ofphysically distinct memory storage devices in a distributed manner toprevent storage of any member of the first set of encoded media segmentstogether with any member of the second set of encoded media segmentsthat has an overlapping partial period of playback time of the mediacontent file.

Another embodiment of an RS-DVR system is also provided here. The RS-DVRsystem includes a network interface to communicate data between theRS-DVR system and a subscriber system via a network, a file systemmodule coupled to the network interface, an ingest agent coupled to thefile system module to receive encoded media segments that represent amedia content file encoded at a plurality of different bitrates, and astorage architecture coupled to the file system to store the encodedmedia segments as a single logical file.

Also presented here is a related embodiment of a method of operating anRS-DVR system that supports a subscriber system via data communicationover a network. The method receives, at the RS-DVR system, encoded mediasegments that represent different versions of a media content fileencoded at a plurality of different bitrates. The method also receives,at the RS-DVR system, an instruction to record the media content file onbehalf of a subscriber. In response to receiving the instruction, themethod stores the encoded media segments as a single logical file acrossa plurality of memory storage devices of the RS-DVR system.

Also provided is another method of operating an RS-DVR system thatsupports a subscriber system via data communication over a network. Themethod begins by receiving, at the RS-DVR system, encoded media segmentsthat represent different versions of a media content file encoded at aplurality of different bitrates, along with an instruction to record themedia content file on behalf of a subscriber. In response to receivingthe instruction, the method stores the encoded media segments in astorage architecture as a single logical file, wherein the singlelogical file has a file structure arranged such that data representingencoded media segments for any particular bitrate is contiguous withinthe file structure.

The following disclosure also presents another method of operating anRS-DVR system that supports a plurality of subscriber systems via datacommunication over a network. The method receives a media content fileat the RS-DVR system, and stores a plurality of recorded versions of themedia content file in a storage architecture of the RS-DVR systemwithout assigning any of the plurality of recorded versions of the mediacontent file to any of the plurality of subscriber systems, resulting ina pool of unassigned recorded versions of the media content file. Themethod continues by maintaining the pool of unassigned recorded versionsof the media content file until receiving at least one request forplayback of the media content file.

Also provided is another embodiment of an RS-DVR system having a networkinterface to communicate data between the RS-DVR system and a pluralityof subscriber systems via a network, a file system module coupled to thenetwork interface, an ingest agent coupled to the file system module toreceive a media content file, and a storage architecture coupled to thefile system to store a plurality of recorded versions of the mediacontent file without assigning any of the plurality of recorded versionsof the media content file to any of the plurality of subscriber systems,resulting in a pool of unassigned recorded versions of the media contentfile. The file system module and the storage architecture cooperate toassign the unassigned recorded versions of the media content file to theplurality of subscriber systems in response to receiving requests forplayback of the media content file.

Another embodiment of a method of operating an RS-DVR system thatsupports a plurality of subscriber systems via data communication over anetwork begins by receiving a media content file at the RS-DVR system.The method continues by estimating a number of playback requests for themedia content file to be received from the plurality of subscribersystems, resulting in a predicted number. The method continues bystoring recorded versions of the media content file in a storagearchitecture of the RS-DVR system without assigning any of the recordedversions of the media content file to any of the plurality of subscribersystems, resulting in a pool of unassigned recorded versions of themedia content file, wherein the pool includes at least the predictednumber of unassigned recorded versions of the media content file. Themethod continues by assigning, at the RS-DVR system, the unassignedrecorded versions of the media content file to the plurality ofsubscriber systems upon receipt of requests for playback of the mediacontent file.

Yet another embodiment of an RS-DVR system is also provided. The RS-DVRsystem includes a network interface to communicate data between theRS-DVR system and a plurality of subscriber systems via a network, afile system module coupled to the network interface, an ingest agentcoupled to the file system module to receive encoded media segments thatrepresent media content files encoded at a plurality of differentbitrates, and a plurality of memory storage devices coupled to the filesystem to store the encoded media segments. Each of the plurality ofmemory storage devices is divided into a plurality of allocation unitsto store the encoded media segments, and each of the plurality of memorystorage devices stores a respective index table comprising entries forat least some of the plurality of allocation units. Moreover, each ofthe entries includes descriptive data that characterizes one or moreencoded media segments stored in the respective allocation unit.

Also provided is an embodiment of a method of operating an RS-DVR systemthat supports a plurality of subscriber systems via data communicationover a network. The method begins by receiving, at the RS-DVR system,encoded media segments that represent media content files encoded at aplurality of different bitrates. The method stores the encoded mediasegments in a plurality of memory storage devices of the RS-DVR system,each of the plurality of memory storage devices being divided into aplurality of allocation units to store the encoded media segments. Themethod continues by maintaining, at each of the plurality of memorystorage devices, a respective index table comprising entries for atleast some of the plurality of allocation units. Each of the entriesincludes descriptive data that characterizes one or more encoded mediasegments stored in the respective allocation unit.

Also provided is another embodiment of a method of operating an RS-DVRsystem that supports a plurality of subscriber systems via datacommunication over a network. The method receives, at the RS-DVR system,encoded media segments that represent media content files encoded at aplurality of different bitrates, and stores the encoded media segmentsin a plurality of allocation units of a memory storage device. Themethod continues by generating an index table for the memory storagedevice, the index table including a respective entry for each of theplurality of allocation units having an encoded media segment storedtherein. Each entry of the index table includes a content identifierthat identifies a particular one of the media content files, a bitrateidentifier that identifies one of the plurality of different bitrates,and a time index relative to the particular one of the media contentfiles. The method continues by storing the index table in the memorystorage device.

Also presented here is an embodiment of an RS-DVR system having anetwork interface to communicate data between the RS-DVR system and asubscriber system via a network, a file system module coupled to thenetwork interface, an ingest agent coupled to the file system module toreceive media content files, the media content files including sharedrights media content files and per-subscriber rights media contentfiles, a shared storage architecture coupled to the file system to storethe shared rights media content files, and a per-subscriber storagearchitecture coupled to the file system to store the per-subscriberrights media content files.

Also presented here is an embodiment of a method of operating an RS-DVRsystem that supports a plurality of subscriber systems via datacommunication over a network. The method receives, at the RS-DVR system,shared rights media content files and per-subscriber rights mediacontent files, and stores the shared rights media content files in ashared storage architecture of the RS-DVR system. The method continuesby storing the per-subscriber rights media content files in aper-subscriber storage architecture of the RS-DVR system.

Also presented here is an embodiment of a method of operating an RS-DVRsystem that supports a subscriber system via data communication over anetwork. The method begins by receiving, at the RS-DVR system, mediacontent files. The method continues by obtaining, at the RS-DVR system,an instruction to record a requested media content file, and bydetermining, at the RS-DVR system, whether the requested media contentfile has shared rights or per-subscriber rights. The method continues bystoring the requested media content file in a shared storagearchitecture of the RS-DVR system when the determining step determinesthat the requested media content file has shared rights, and by storingthe requested media content file in a per-subscriber storagearchitecture of the RS-DVR system when the determining step determinesthat the requested media content file has per-subscriber rights.

This summary is provided to introduce a selection of concepts in asimplified form that are further described below in the detaileddescription. This summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended tobe used as an aid in determining the scope of the claimed subjectmatter.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the subject matter may be derived byreferring to the detailed description and claims when considered inconjunction with the following figures, wherein like reference numbersrefer to similar elements throughout the figures.

FIG. 1 is a schematic representation of an exemplary embodiment of avideo services system;

FIG. 2 is a simplified schematic representation of an exemplarycomputer-based implementation of an embodiment of an RS-DVR system;

FIG. 3 is a schematic representation of an exemplary embodiment of anRS-DVR system;

FIG. 4 is a schematic representation of a media content file;

FIG. 5 is a schematic representation of media content streams;

FIG. 6 is a schematic representation of a media content stream dividedinto a plurality of media segments;

FIG. 7 is a schematic representation of encoded media segmentscorresponding to a media content file;

FIG. 8 is a flow chart that illustrates an exemplary embodiment of aprocess for operating an adaptive rate RS-DVR system;

FIG. 9 is a flow chart that illustrates an exemplary embodiment of anunavailable bitrate signaling process;

FIG. 10 is a flow chart that illustrates an exemplary embodiment of aprocess for operating an RS-DVR system;

FIG. 11 is a flow chart that illustrates an exemplary embodiment of alate assignment process of an RS-DVR system;

FIG. 12 is a diagram that depicts an exemplary embodiment of an indextable that includes descriptive data related to media segments stored ona memory storage device;

FIG. 13 is a diagram that depicts an exemplary embodiment of anallocation unit having consistency check fields; and

FIG. 14 is a diagram that depicts encoded media segments correspondingto a media content file.

DETAILED DESCRIPTION

The following detailed description is merely illustrative in nature andis not intended to limit the embodiments of the subject matter or theapplication and uses of such embodiments. As used herein, the word“exemplary” means “serving as an example, instance, or illustration.”Any implementation described herein as exemplary is not necessarily tobe construed as preferred or advantageous over other implementations.Furthermore, there is no intention to be bound by any expressed orimplied theory presented in the preceding technical field, background,brief summary or the following detailed description.

Techniques and technologies may be described herein in terms offunctional and/or logical block components, and with reference tosymbolic representations of operations, processing tasks, and functionsthat may be performed by various computing components or devices. Suchoperations, tasks, and functions are sometimes referred to as beingcomputer-executed, computerized, software-implemented, orcomputer-implemented. Accordingly, it should be appreciated that thevarious block components shown in the figures may be realized by anynumber of hardware, software, and/or firmware components configured toperform the specified functions. For example, an embodiment of a systemor a component may employ various integrated circuit components, e.g.,memory elements, digital signal processing elements, logic elements,look-up tables, or the like, which may carry out a variety of functionsunder the control of one or more microprocessors or other controldevices.

Certain functions and operations of an RS-DVR system are described belowwith reference to figures that depict processes in the form of flowcharts. In this regard, the various tasks performed in connection with adescribed process may be performed by software, hardware, firmware, orany combination thereof In practice, portions of a described process maybe performed by different elements of the described RS-DVR system. Itshould be appreciated that a described process may include any number ofadditional or alternative tasks, the tasks shown in a given figure neednot be performed in the illustrated order, and that a described processmay be incorporated into a more comprehensive procedure or processhaving additional functionality not described in detail herein.Moreover, one or more of the tasks shown in a flow chart figure could beomitted from an embodiment of the illustrated process as long as theintended overall functionality remains intact.

FIG. 1 is a schematic representation of an exemplary embodiment of avideo services system 100. The video services system 100 generallyincludes, without limitation: at least one subscriber system 102 and atleast one RS-DVR system 104 that communicates with the subscribersystems 102. Although not always required, the illustrated embodiment ofthe system 100 includes an RS-DVR manager 106 to manage, control, orotherwise regulate the operation of the RS-DVR systems 104. Each RS-DVRsystem 104 is in data communication with one or more of the subscribersystems 102. In this regard, the system 100 may include or cooperatewith a data communication network 108 that facilitates communication ofmedia content from the RS-DVR systems 104 to the subscriber systems 102.

A subscriber system 102 may be realized in any number of different ways,and it may be suitably configured as needed to perform any number ofdesired functions, e.g., the presentation of media content, which may beaudio content, video content, or audio-visual content. For example, asubscriber system 102 may be implemented as any of the following,without limitation: a computing device; a video game device; a telephonedevice (wireless or traditional); an electronic medical device; ahousehold or other electronic appliance; a digital media player device;a digital media place-shifting device; a television set; a set top boxfor a video services receiver; stereo or other entertainment equipment;an alarm clock; or the like. These examples are not intended to limit orotherwise restrict the scope of the embodiments described herein.

The network 108 is any digital or other communications network capableof transmitting messages between the subscriber systems 102 and theRS-DVR manager 106 (or, for embodiments that lack the RS-DVR manager106, between the subscriber systems 102 and the RS-DVR systems 104). Invarious embodiments, the network 108 includes any number of public orprivate data connections, links or networks supporting any number ofcommunications protocols. The network 108 may include the Internet, forexample, or any other network based upon IP or other data deliverprotocols. In various embodiments, the network 108 also incorporates awireless and/or wired telephone network, such as a cellularcommunications network for communicating with mobile phones, personaldigital assistants, and/or the like. The network 108 also incorporateany sort of wireless or wired local area networks, such as one or moreIEEE 802.3 and/or IEEE 802.11 networks.

The RS-DVR manager 106 may be implemented as a server that manages adesignated group of RS-DVR systems 104. Although only one RS-DVR manager106 is depicted in FIG. 1, an embodiment of the video services system100 could include more than one RS-DVR manager 106 to handle any numberof defined groups of RS-DVR systems 104. Each RS-DVR system 104 isconfigured to receive digital media content in a multiple bitrateformat, record one or more versions of the media content on behalf ofthe subscriber systems 102, and initiate playback of stored mediacontent at the request of the subscriber systems 102. Exemplaryembodiments of the RS-DVR system 104, along with various operatingfeatures and functions, are described in detail below.

In accordance with one practical deployment, an RS-DVR system 104provides centralized “cloud” or multiple system operator (MSO) hostedrecording and playback of linear television channels. The RS-DVR system104 can be designed to function like a traditional DVR, wherein eachsubscriber has a “personal” copy of recorded content, even though thecopies are held on shared servers and shared storage media (e.g., harddisks).

With RS-DVR capabilities, a video services entity can provide a unifieduser experience in accessing live linear, start over, recorded andvideo-on-demand (VOD) video. The actual delivery path can vary bychannel and by program depending on the granted content rights. Forexample, content with start over or time shifting or VOD rights from thepublisher can use a single copy of the content in shared storage. For“DVR-like” playback of content without shared recording rights, RS-DVRservers are used. Continuous “Start Over” on multiple channels is a newand useful capability that in the past was not feasible to provide usinga DVR approach, but which now is possible using RS-DVR systems 104.RS-DVR systems also allow the subscriber to record at the same time avirtually unlimited number of linear television channels and programs,whereas conventional DVRs typically only allow for one or two.

In certain embodiments, the video services system 100 handles adaptiverate (or multiple bitrate) digital media content. Accordingly, theRS-DVR systems 104 are preferably configured to support the multiplebitrate scheme by recording a plurality of encoded video bit rates. Incertain implementations, each subscriber has only one copy of therecorded content because the various bit rate versions of the samecontent are stored together in one logical file. As with traditionaladaptive rate approaches, the video is split up into multi-second “mediasegments” and retrieved as HTTP objects. In the context of thisdisclosure, a “media segment” may refer to a segment of audio content, asegment of video content, a segment of audio-visual content, or thelike.

The adaptive rate RS-DVR system 104 can be implemented as a specializedweb server that records and retrieves video files on behalf of anynumber of subscriber systems 102. The RS-DVR system 104 receives videofrom live stream encoders via either a multicast of the encoded mediasegments or via an HTTP GET request methodology. The RS-DVR system 104then immediately makes as many copies of the video as there aresubscribers requesting to record the channel. Each subscriber has, ineffect, their own area that contains their individual copies of thechannel. Each subscriber can have different programs recorded ondifferent RS-DVR systems 104—each individual recording is on only oneserver. On playback, the subscriber system 102 requests video from theappropriate RS-DVR system 104 and specifies which individual subscriberis requesting it (so that the RS-DVR system 104 can find the correctvideo copy). The video is returned to the requesting subscriber system102 from the specialized web server. The HTTP video objects are markedas being non-cacheable to ensure that the personalized video copy isonly delivered to the requesting subscriber system.

In accordance with certain exemplary embodiments, as soon as the videois encoded and sent to the RS-DVR system 104, it is immediatelyseparated into per subscriber copies by being written multiple timesinto separate files in the file system. From then on the video remainsseparate and is only accessible by the individual subscriber thatrequested the recording. In that way the RS-DVR video storage anddelivery scheme does not run afoul of copyright law. In otherembodiments, where copyright law is not of the same concern, the RS-DVRsystem 104 may instead utilize one copy of a particular video formultiple users. For example, one copy may be used for all users ormultiple copies may distributed across multiple storage devices orservers that serve some subset of users.

As mentioned above, the RS-DVR manager 106 can be utilized to support a“cluster group” of RS-DVR systems 104. In practice, there can bemultiple cluster groups with each having one or more RS-DVR systems 104.Depending on the particular system requirements, a cluster group mayinclude up to hundreds of RS-DVR systems 104. A cluster group is used toprovide scalability and creates certain types of failure resiliency.

Each cluster group may be configured to record a set of channels. At thetime the subscriber is provisioned with their channel lineup, eachsubscriber is assigned to a cluster group for each channel that can berecorded on their behalf. The RS-DVR systems 104 within a cluster groupare physically located together. They typically can be deployed withinthe broadband access network close to the subscribers and close to whereContent Delivery Network (CDN) edge HTTP caching servers are located.

The RS-DVR manager 106 may be implemented as one or more servers thatmonitor the status and capacity of each RS-DVR system 104 and clustergroup. The RS-DVR manager 106 assigns a specific RS-DVR system 104within the cluster group to record a specific channel and/or program asper subscriber requests. Any RS-DVR system 104 within the cluster groupis capable of recording any content for any subscriber assigned to thecluster group. The RS-DVR manager 106 makes the actual recordingassignments a function of available capacity and current (and futurescheduled) loads on the individual RS-DVR systems 104.

As described in more detail below, an embodiment of the RS-DVR system104 spreads each recorded video asset across the multiple drives withineach chassis/enclosure. This allows for load balancing and maximumscalability. This also facilities quick recovery of video in the case ofsoft or catastrophic server failures. The RS-DVR system 104 allocateswhat video is recorded where as a function of the individual driveperformance characteristics. It also writes data to the disk drives in away that minimizes head throw. This improves the mean time betweenfailure for the disk drives, yet allows for the drives to be continuallydriven hard. This also allows the RS-DVR systems 104 to use lessexpensive disk drives.

The RS-DVR systems 104 are designed to operate continually at fullcapacity and performance for long periods of time. The RS-DVR systems104 can sustain multiple hard disk failures without causing thesubscriber to lose access to their recorded video. The RS-DVR systems104 need not implement traditional RAID architectures, but instead takeadvantage of the inherent failure resiliency that comes from adaptiverate and multiple bitrate versions of content. Moreover, failed harddisk drives can be “hot swapped” at any time and replaced with differentor new drives. Unlike traditional RAID, upon replacement there is norebuild time. As faster/better drives are added, the RS-DVR system 104will automatically take advantage of the better capabilities, again incontrast to traditional RAID which typically do not.

A practical implementation of the RS-DVR system 104 must contemplatehard disk failures. Unlike traditional DVR systems, where a failed harddisk typically results in lost content, failure of a hard disk of theRS-DVR system 104 does not result in a complete loss. Although lostvideo data is not recovered, there will almost always be a differentbitrate version available on a different disk. Thus, a drive failureonly affects a small portion of a given video recording, preferably onlya single bitrate of each affected portion. In response to a failed diskdrive, the RS-DVR system 104 signals to the subscriber system 102 toswitch to a different bitrate (which will be on a different drive).Multiple hard disk failures will affect more data, but with a givenrecording spread across dozens of drives the impact of even multiplefailures is minimal When a failed drive is “hot swapped” with a newdrive the RS-DVR system 104 instantaneously detects that a new drive isavailable and immediately starts to use it to record video.

SATA drives in particular can, over time, lose some of their originalperformance and speed. The RS-DVR system 104 can detect this phenomenaand start assigning less and less video to a slowing drive. This can bemonitored and at a certain point the RS-DVR system 104 can automaticallyquit writing new video to the drive, which over time will depopulate itand allow for replacement. SATA drives may also intermittently (andtemporarily) become very slow. This could affect playback, when severalsubscribers need video from a particular slowed drive. The RS-DVR system104 under this case will signal the subscriber system 102 to try adifferent bit rate, which results in playback from a different drive.

If an RS-DVR system 104 goes down, upon detecting failure, the RS-DVRmanager 106 immediately assigns active recordings assigned to the failedRS-DVR system 104 to different RS-DVRs within the cluster group. If anRS-DVR system 104 has a hard failure, the system is designed to allowthe hard disks to be immediately connected to a different RS-DVR system104. This could be a standby server or perhaps an operational one thatis ready to receive hard disks. In accordance with certain embodiments,individual asset recordings are not allowed to span multiple diskenclosures. Accordingly, upon re-mount the new RS-DVR system 104 willrestore the content on the disk drives and make the content immediatelyavailable, subject to the limitations previously explained.

It may be useful to locate primary and standby RS-DVR managers 106 indifferent geographic locations, as well as different cluster groups.That way, if a site goes down then the service can at least partiallyremain alive. As soon as network connectivity is restored, the dualRS-DVR managers 106 will see each other and elect one to return tostandby mode. The new singular RS-DVR manager 106 will undo any damageor redundant recordings that the other RS-DVR manager 106 did. With itlikely that extra recordings were scheduled, the damage will be minimalor non-existent and the recovery will be very straight forward andtypically not perceivable by the subscriber.

In accordance with one implementation, the RS-DVR systems 104 aredeployed by MSOs close to the edge of their network, at roughly the samelocation where HTTP caching is provided. The RS-DVR systems 104 would bedeployed at that location because the content delivered by the RS-DVRsystems 104 is required to be “non-cacheable” and video deliverytypically works better if the content comes from a system that is“close” to the subscriber.

An important consideration in planning on where to deploy RS-DVR clustergroups is the cost of the back haul bandwidth. Every channel beingrecorded by the cluster group requires back haul bandwidth for all ofthe bitrates, which suggests that the RS-DVR cluster groups should becentralized. However, with the streams being delivered to the subscriberfrom the RS-DVR systems 104 being marked as non-cacheable, depending onhow many subscribers there are at peak load times it could be better tolocate the RS-DVR cluster groups closer to the subscriber, to avoidusing back haul bandwidth for subscriber playback. It is thereforerecommended that the RS-DVR systems 104 be deployed both centrally andat the edge with the centralized RS-DVR systems 104 being utilized forcontent where the amount of bandwidth required for actual playback willbe less than the bandwidth required to send the multiple copies down tothe edge RS-DVR systems 104. The RS-DVR manager 106 will use actualplayback analytics in deciding where to assign particular recordings.

Referring again to the drawings, FIG. 2 is a simplified schematicrepresentation of an exemplary computer-based implementation of anembodiment of an RS-DVR system 200. The RS-DVR system 200 is only oneexample of a suitable implementation and is not intended to suggest anylimitation as to the scope of use or functionality of the RS-DVR systems104. For example, although the RS-DVR system 200 is depicted as aunitary component, a practical implementation may include a plurality ofphysical hardware components that cooperate in a distributedarchitecture.

The RS-DVR system 200 and certain aspects thereof may be described inthe general context of computer-executable instructions, such as programmodules, executed by one or more processors or other devices. Generally,program modules include routines, programs, objects, components, datastructures, and/or other elements that perform particular tasks orimplement particular abstract data types. Typically, the functionalityof the program modules may be combined or distributed as desired invarious embodiments.

The RS-DVR system 200 typically includes at least some form of computerreadable media. Computer readable media can be any available media thatcan be accessed by the RS-DVR system 200 and/or by applications executedby the RS-DVR system 200. By way of example, and not limitation,computer readable media may comprise computer storage media thatincludes volatile, nonvolatile, removable, and non-removable mediaimplemented in any method or technology for storage of information suchas computer readable instructions, data structures, program modules orother data. Computer storage media includes, but is not limited to, RAM,ROM, EEPROM, flash memory or other memory technology, CD-ROM, digitalversatile disks (DVD) or other optical storage, magnetic cassettes,magnetic tape, magnetic disk storage or other magnetic storage devices,or any other medium which can be used to store the desired informationand which can accessed by the RS-DVR system 200.

Referring again to FIG. 2, in its most basic configuration, the RS-DVRsystem 200 typically includes at least one processing unit 202 and asuitable amount of memory 204. This most basic configuration isidentified in FIG. 2 by reference number 206. The processing unit 202and the memory 204 cooperate to provide the desired functionality,processing logic, and operating intelligence for the RS-DVR system 200,as described in more detail below. Depending on the exact configurationand type of RS-DVR system 200, the memory 204 may be volatile (such asRAM), non-volatile (such as ROM, flash memory, etc.) or some combinationof the two. The RS-DVR system 200 may also include additional storage(removable and/or non-removable) including, but not limited to, magneticor optical disks or tape. Such additional storage is illustrated in FIG.2 by removable storage 208 and non-removable storage 210. The memory204, the removable storage 208, and the non-removable storage 210 areall examples of computer storage media as defined above.

The RS-DVR system 200 may also contain communications connection(s) 212that allow the system 200 to communicate with other devices, such as theRS-DVR manager 106 or the subscriber systems 102 shown in FIG. 1. TheRS-DVR system 200 may also include or communicate with input device(s)214 such as a keyboard, mouse or other pointing device, pen, voice inputdevice, touch input device, etc. The RS-DVR system 200 may also includeor communicate with output device(s) 216 such as a display, speakers,indicator lights, a printer, or the like.

FIG. 3 is another schematic representation of an exemplary embodiment ofan RS-DVR system 300. FIG. 3 depicts some of the primary logical orfunctional modules of the RS-DVR system 300. The illustrated embodimentof the RS-DVR system 300 generally includes, without limitation: aprocessing logic module 302; a network interface (which in thisexemplary embodiment is realized as a web server 304); a file systemmodule 306; an ingest agent 308; and a storage architecture 310 (whichin this exemplary embodiment is realized as a plurality of memorystorage devices such as hard disk drives). These elements cooperate tosupport the various functions and operations of the RS-DVR system 300.

The processing logic module 302 may cooperate with the web server 304,the file system module 306, the ingest agent 308, and the storagearchitecture 310 as needed during operation of the RS-DVR system 300.Moreover, the processing logic module 302 may be suitably configured tosupport one or more designated functions of the RS-DVR system 300. Inthis regard, the processing logic module 302 may include any desiredfunctionality. For example, the processing logic module 302 may bedesigned to include a content rights management module, a hard diskmonitor module, a diagnostic module, or the like.

The web server 304 (and/or any suitable network interface) representshardware, software, firmware, and/or logic that is configured tocommunicate data between the RS-DVR system 300 and another component orelement such as a subscriber system. Referring to FIG. 1, the web server304 can be used to deliver media content to the subscriber systems 102via the network 108. The arrow 312 in FIG. 3 represents the datacommunication link between the web server 304 and the network 108. Incertain embodiments, the web server 304 cooperates with the file systemmodule 306 to provide media content files (in the form of encoded mediasegments) to the subscriber systems 102 in accordance with establishedHTTP techniques and methodologies.

The file system module 306 is utilized to manage, organize, and maintainfiles in the storage architecture 310. As explained in more detailbelow, the file system module 306 can be written to accommodate multiplebitrate encoded media segments that are stored in a distributed manneracross a plurality of hard disks of the storage architecture 310. Thefile system module 306 also cooperates with the ingest agent 308 toaccommodate the recording and storage of encoded media segments asneeded during the operation of the RS-DVR system 300. The ingest agent308 may be coupled to the file system module 306 to receive encodedmedia segments that represent media content files encoded at a pluralityof different bitrates. The ingest agent 308 is capable of receivingmulticast delivered media segments 316 and/or unicast delivered mediasegments 318 from an appropriate content source. One suitable type ofcontent source that provides multiple bitrate encoded media segments isdescribed in U.S. Pat. No. 7,818,444, the content of which isincorporated by reference herein.

The storage architecture 310 is coupled to the file system module 306 tostore encoded media segments that can be subsequently accessed forplayback to one or more subscriber systems. In certain implementations,the storage architecture 310 includes a plurality of memory storagedevices such as hard disk drives. The memory storage devices arephysically distinct and separate units that can be removed and replacedas needed. The file system module 306 governs the manner in which theencoded media segments are stored in the different memory storagedevices, as explained in more detail below.

During operation, the processing logic module 302, web server 304, filesystem module 306, ingest agent 308, and storage architecture 310cooperate to carry out content recording, content file (media segment)storing, file management, disk management, content playback, and otherfunctions of the RS-DVR system 300. For the multiple bitrateimplementation described here, these elements of the RS-DVR system 300cooperate to provide stored media segments to the subscriber systems 102for presentation using at least one of the plurality of differentavailable bitrates.

Multiple Bitrate Media Segments

FIG. 4 a is a schematic representation of an exemplary media contentfile 400, which may correspond to an audio or video program, clip,segment, movie, or the like. The content file 400 may be distributed bya publisher or source for purposes of broadcast or unicast distributionvia a video services system. The actual subject matter of the contentfile 400 (although unimportant for purposes of this description) maycomprise a television broadcast, sports event, movie, music, concert,etc. The content file 400 may be live or archived content. The contentfile 400 may comprise uncompressed video and audio, or alternatively,video or audio. Alternatively, the content file 400 may be compressedusing standard or proprietary encoding schemes.

FIG. 5 is a schematic representation of a plurality of streams 402having varying degrees of quality and bandwidth. In one embodiment, theplurality of streams 402 comprises a low quality stream 404, a mediumquality stream 406, and a high quality stream 408. Each of the streams404, 406, 408 represents a copy or a version of the content file 400(see FIG. 4) encoded and compressed to varying bitrates. For example,the low quality stream 404 may be encoded and compressed to a bitrate of100 kilobits per second (kbps), the medium quality stream 406 may beencoded and compressed to a bitrate of 200 kbps, and the high qualitystream 408 may be encoded and compressed to 600 kbps.

FIG. 6 is a schematic representation of a media content stream 420divided into a plurality of source media segments 422. As used herein,“media segment” refers to any sized portion of the content file 400.Each media segment 422 may comprise a portion of the content containedin the stream 420, encapsulated as an independent media object. Thecontent in a media segment 422 may have a unique time index in relationto the beginning of the content contained in the stream 420. In oneembodiment, the content contained in each media segment 422 may have aduration of two seconds. For example, media segment 0 may have a timeindex of 00:00 representing the beginning of content playback, and mediasegment 1 may have a time index of 00:02, and so on. Alternatively, thetime duration of the media segments 422 may be any duration that is lessthan the entire playback duration of the content in the stream 420. In afurther embodiment, the media segments 422 may be divided according tofile size instead of a time index and duration.

FIG. 7 is a schematic representation of encoded media segmentscorresponding to the media content file 400. FIG. 7 depicts differentsets 430 of media segments, where a “set” refers to a group of mediasegments having identical time indices and durations but varyingbitrates. In the depicted embodiment, the set 430 a encompasses allmedia segments having a time index of 00:00. The set 430 a includesencoded media segments 434 having low, medium, and high bitrates(identified by reference numbers 404, 406, 408). Of course, each set 430may include more than the depicted three bitrates which are given by wayof example only. One skilled in the art will recognize that any numberof streams having different bitrates may be generated from the originalcontent file 400.

As described above, the duration of one media segment 434 may beapproximately two seconds. Likewise, each set 430 may comprise aplurality of media segments 434 where each media segment 434 has aplayable duration of two seconds. Alternatively, the duration of a mediasegment 434 may be predetermined or dynamically variable depending upona variety of factors including, but not limited to, network congestion,system specifications, playback resolution and quality, etc. In thedepicted embodiment, the content file 400 may be collectively formed ofthe plurality of sets 430. The number of sets 430 may depend on thelength of the content file 400 and the length or duration of each mediasegment 434.

Referring again to FIG. 3, the ingest agent 308 receives media contentfiles in the form of a plurality of encoded media segments thatcorrespond to a plurality of different bitrates. In other words, foreach media content file to be recorded by the RS-DVR system 300, theingest agent 308 receives the various encoded media segments associatedwith the different time indices and the different bitrates.

Basic RS-DVR Operation

Referring now to FIG. 8, an exemplary embodiment of a process 500 foroperating an adaptive rate RS-DVR system will be described. As describedpreviously, the RS-DVR system supports one or more subscriber systemsvia data communication over a network such as the Internet. The RS-DVRsystem receives encoded media segments that represent one or more mediacontent files encoded at a plurality of different bitrates (task 502).In certain implementations, each media content file is encoded at tendifferent bitrates, and each media segment represents a two-secondsegment of the media content file, as explained above. However, it is tobe appreciated that any number of encoded bit rates may be utilizeddepending on desired design criteria, such as available bandwidth,supported devices and the like. Accordingly, the encoded media segmentsreceived by the RS-DVR system preferably include different sets ofencoded media segments corresponding to the different bitrates.

If any given media content file is to be recorded (query task 504), thenthe RS-DVR system stores the encoded media segments for that particularmedia content file in the storage architecture of the RS-DVR system(task 506). A given media content file could be stored any number oftimes if so desired. For example, it may be desirable or required tostore a first instantiation of the encoded media segments on behalf of afirst subscriber, a second instantiation of the encoded media segmentson behalf of a second subscriber, and so on. Alternatively (oradditionally), it may be desirable or allowable to store a sharedinstantiation of the encoded media segments on behalf of a plurality ofdifferent subscribers.

In certain embodiments, media content files are recorded and stored atthe request of a subscriber or a subscriber system. Thus, query task 504may determine whether the RS-DVR system receives an instruction torecord the media content file on behalf of a subscriber. For example, arecording instruction or request may be received at the RS-DVR system inthe form of an HTTP request from one of the subscriber systems.Alternatively, some or all media content files could be automaticallyrecorded by the RS-DVR system in a manner that does not require anyinstructions, commands, or requests from the subscriber systems. In thisregard, the RS-DVR system could be configured to record all availablecontent at all of the different bitrates to provide instant start-overfunctionality for the end users. In other words, the RS-DVR system couldrecord and store multiple bitrate media segments corresponding to allprogramming available from a video services provider and for allusers/subscribers of the video services provider. Although storage spacemay represent a practical limitation of this “catch-all” approach, ifonly a limited period of time is recorded (e.g., the last three or fourhours), then the approach is viable and realistic.

In certain embodiments, the storage architecture is realized as aplurality of distinct and separate memory storage devices (e.g., harddisk drives). The use of multiple storage devices allows the RS-DVRsystem to store the media segments for any given media content file in adistributed manner across the plurality of memory storage devices. Thus,if one of the storage devices fails or is otherwise unable to supportsatisfactory delivery of its stored media segments, the entire mediacontent file is not lost. Moreover, the use of multiple storage devicesallows the RS-DVR system to distribute the stored media segments fordifferent subscriber systems. For instance, task 506 may be controlledor managed such that each of the plurality of different memory storagedevices maintains stored media segments for a plurality of differentsubscriber systems. Alternatively, an embodiment of the RS-DVR systemcould assign memory storage devices on a per-subscriber basis.

The RS-DVR system can maintain stored media segments for any amount oftime. The illustrated embodiment of the process 500 checks whether arequest for playback of a stored media content file is received at theRS-DVR system (query task 508). In response to receiving a playbackrequest, the RS-DVR system provides stored media segments to therequesting subscriber system (via the network) for presentation orplayback at the requesting subscriber system (task 510). Thus, theencoded media segments provided to the requesting subscriber systemcorrespond to the requested media content file encoded at a requestedbitrate. For the exemplary embodiment described here, a playback requestincludes or takes the form of an HTTP GET request that originates at therequesting subscriber system and is received at the web server of theRS-DVR system. In practice, each HTTP GET request may include orotherwise indicate the particular media content file to be played back,a user identifier that identifies the requesting subscriber systemand/or the requesting user, a requested bitrate for the media contentfile, a time index or time range associated with one or more mediasegments, and any other information that might be needed to enable theRS-DVR system to locate and access the appropriate stored mediasegments.

Unavailable Bitrate Signaling

As mentioned above with reference to the RS-DVR operating process 500, asubscriber system can request playback of a media content file at adesignated bitrate. In certain situations, it may not be possible forthe RS-DVR system to provide some or all of the encoded media segmentsat the requested bitrate. This might occur, for example, if a memorystorage device has failed, is too overloaded, or has experienced aslowdown in its operating speed. If the bitrate for one or morerequested media segments is not available, then the RS-DVR system cantake appropriate action to ensure that the subscriber does notexperience an interruption in service.

FIG. 9 is a flow chart that illustrates an exemplary embodiment of anunavailable bitrate signaling process 520, which may be performed by anRS-DVR system of the type described herein. The process 520 receives aplayback request that identifies a requested bitrate for a given mediacontent file (task 522). If the requested bitrate is available (the “NO”branch of query task 524), then the RS-DVR system provides the storedmedia segment(s) at the requested bitrate (task 526) and continues toreceive additional playback requests as usual.

If query task 524 determines that the requested bitrate is unavailable,then the RS-DVR system may generate and send one or more messages,notifications, codes, or the like. For example, in certain embodimentsthe web server of the RS-DVR system generates and sends an HTTP statuscode to indicate that the requested bitrate for the requested mediacontent file is unavailable at the RS-DVR system (task 528). Dependingupon the particular implementation, the RS-DVR system could use astandard HTTP code (such as HTTP status code 204) to indicate theunavailable bitrate, or it could use a custom or system-specific statuscode to indicate the unavailable bitrate. As an alternative to task 528(or in addition to task 528), the RS-DVR system could generate and senda message that identifies or lists any available bitrates for therequested media content file (task 530). This approach could result inless “trial and error” on the part of the subscriber system, especiallyif more than one bitrate is unavailable at the RS-DVR system. As anotheralternative to task 528 (or in addition to task 528), the RS-DVR systemcould generate and send a message that instructs the subscriber systemto select and request another bitrate (task 532). In other words, theRS-DVR system prompts the requesting subscriber system to choose abitrate that is different than the previously requested bitrate.

The approaches described above assume that the video services systemprefers to have the subscriber system specify and request the desiredbitrate. In certain embodiments, however, the RS-DVR system couldautomatically select a different bitrate and provide the correspondingmedia segments to the subscriber system when the requested bitrate isunavailable. In other words, the dynamic switching of bitrates may beperformed in a way that is transparent to the subscriber system. Suchautomatic selection of a different bitrate could be performed inconjunction with any of the signaling techniques mentioned above. Forexample, the RS-DVR system could provide media segments at anon-requested bitrate to ensure seamless content delivery whileconcurrently informing the requesting subscriber system of the newbitrate and/or while concurrently asking the requesting subscribersystem to select a different bitrate going forward.

Shared And Per-Subscriber Storage Of Media Content Files

A traditional DVR system that is owned or leased by a subscriber forpersonal operation will record individual copies of media content forthe personal and exclusive use by that particular subscriber. As anextension of this concept, an RS-DVR system of the type described hereis capable of recording and storing encoded media segments for mediacontent files such that each subscriber has its own storage spacemaintained by the RS-DVR system. Consequently, any given media contentfile would be redundantly recorded by the RS-DVR system to provide anindividually assigned copy of that media content file to each subscribersystem. In certain situations, however, the RS-DVR system may bepermitted to share a single instantiation of a stored media content filewith a plurality of different subscribers. For example, some contentproducers or content publishers may grant shared access rights or publicdistribution rights to their media content; such media content need notbe redundantly stored to support multiple subscribers. For this reason,it would be desirable to have a single RS-DVR system that functions in ahybrid manner to support both shared and per-subscriber copies of mediacontent files.

Referring again to FIG. 3, the ingest agent 308 of the RS-DVR system 300may be suitably configured to receive media content files having sharedaccess rights associated therewith (i.e., “shared rights media contentfiles”) and/or media content files having per-subscriber access rightsassociated therewith (i.e., “per-subscriber rights media contentfiles”). In this regard, the processing logic module 302 may include orcooperate with a content rights management module (not separately shownin FIG. 3) to determine whether a received media content file has sharedrights or per-subscriber rights associated therewith, and/or todetermine whether a subscriber system (or, equivalently, a subscriber)has shared rights or per-subscriber rights to access a stored mediacontent file.

The storage architecture 310 of the RS-DVR system 300 may include ashared storage architecture to store shared rights media content files,and a per-subscriber storage architecture to store per-subscriber rightsmedia content files. In certain implementations, the shared storagearchitecture exclusively stores shared rights media content fileswithout storing any per-subscriber rights media content files, and theper-subscriber storage architecture exclusively stores per-subscriberrights media content files without storing any shared rights mediacontent files. Moreover, the shared storage architecture and theper-subscriber architecture are preferably realized as physicallydistinct and separated hardware devices, e.g., two separate hard diskdrives, two separate disk drive enclosures, or the like. Notably, theuse of two types of storage enables a single instantiation of the RS-DVRsystem 300 to handle the storage of different content types and tocontemplate use with shared rights content only, per-subscriber rightscontent only, or a hybrid of both.

FIG. 10 is a flow chart that illustrates an exemplary embodiment of aprocess 540 for operating an RS-DVR system that supports at least twostorage architectures for maintaining shared content and per-subscribercontent. The RS-DVR system receives media content files (task 542); themedia content files may be in the form of encoded media segmentscorresponding to different bitrates, as described above. If any givenmedia content file is to be recorded (query task 544), then the RS-DVRsystem determines whether the media content file has shared rights orper-subscriber rights associated therewith (query task 546). Asmentioned above with reference to the process 500 depicted in FIG. 8,the recording of media content files may be initiated by a subscribersystem by sending a suitably formatted instruction to the RS-DVR system.Alternatively, recording may be automatically initiated at the RS-DVRsystem.

If the RS-DVR system determines that the media content file has sharedrights, then the media content file is stored in the shared storagearchitecture of the RS-DVR system (task 548). If, however, the mediacontent file does not have shared subscriber rights, then the mediacontent file is stored in the per-subscriber storage architecture (task550). In certain embodiments, the shared and per-subscriber storagearchitectures are managed and controlled in an ongoing manner such thatthe shared storage architecture exclusively stores media content fileshaving shared rights, and such that the per-subscriber storagearchitecture exclusively stores media content files havingper-subscriber rights.

The RS-DVR system can maintain stored media content files for any amountof time, whether or not a subscriber system requests playback. Theillustrated embodiment of the process 540 checks whether a request forplayback of a stored media content file is received at the RS-DVR system(query task 552). If no playback request is received, then the process540 may exit, return to task 542 to continue receiving media contentfiles, wait for a playback request, or take any appropriate action. Thisexample assumes that a playback request is received. In response toreceiving a playback request, the RS-DVR system determines whether therequested media content file has shared rights or per-subscriber rights(query task 554). Alternatively or additionally, the process 540 maycheck whether the requesting subscriber system or the requesting userhas shared or per-subscriber access rights. The requested media contentfile is accessed from the shared storage architecture (task 556) or fromthe per-subscriber storage architecture (task 558) as appropriate. Theaccessed media content file can then be provided to the requestingsubscriber system for playback (task 560).

Late Assignment Of Recorded Content

A DVR system that services multiple subscriber systems (such as anRS-DVR system) may record programs on demand at the request of thesubscriber systems and/or at the request of the subscribers via somemeans other than the subscriber systems themselves. Thus, when asubscriber records a program, the corresponding recorded media contentfile is assigned to that particular subscriber at the time of recording.Such one-to-one file assignment can be used to ensure that only onesubscriber (i.e., the one that requested recording) can access anystored media content file. Although this one-to-one approach isintuitive and easy to implement, it can result in wasted storage spacewhen a large volume of programs are recorded but never played back.

As an alternative to the typical one-to-one file storage approach, anRS-DVR system as described here may employ a late assignment or “latebinding” scheme that does not assign recorded media content files tosubscribers at the time of recording. Rather, the late assignment schemeassigns recorded media content files to subscribers at the time ofplayback. After a recorded media content file is assigned to a givensubscriber in this manner, that subscriber can request playback of thatmedia content file on his or her subscriber system (or, if thatparticular subscriber owns multiple “eligible” subscriber systems,playback to any eligible subscriber system may be requested). To supporta plurality of different subscribers, multiple copies of a given mediacontent file can still be created and stored in a “pool” that is used toserve copies of the stored content at the time of playback request. Inthis regard, the storage architecture 310 of the RS-DVR system 300 shownin FIG. 3 could be used to anticipatorily store a plurality of recordedversions of a given media content file without actually assigning any ofthe recorded versions to any of the subscribers. The reserved pool ofrecorded copies can be maintained in the storage architecture 310 in anunassigned state until a subscriber system or a subscriber requestsplayback. The file system module 306 and the storage architecture 310can therefore cooperate to assign recorded versions of media contentfiles to the subscribers in response to receiving requests for playback.

FIG. 11 is a flow chart that illustrates an exemplary embodiment of alate assignment process 580, which may be performed by an RS-DVR systemof the type described here. The RS-DVR receives a media content file(task 582) that is subject to recording. The media content file may bein the form of encoded media segments corresponding to differentbitrates, as described above. For simplicity, the process 580 isdescribed for only one media content file. In practice, however, theprocess 580 can be performed to record any number of different mediacontent files.

For this particular embodiment, the RS-DVR system estimates the futureplayback demand for the media content file (task 584). In this regard,the RS-DVR system may estimate the amount of playback requests for themedia content file to be received from different subscribers. Thepredicted number of playback requests can then be used to determine howmany instantiations of the media content file should be saved. Inpractice, the estimation performed by the RS-DVR system could be basedon any number of factors, metrics, or parameters. For example, thepredicted number of playback requests may be based upon usage statisticsfor the plurality of subscribers and/or usage statistics for thesubscriber systems, e.g., recording and playback statistics for thedifferent subscribers, the frequency of playback for similar content,the frequency of playback for content delivered on certain channels, thepopularity of the genre of the media content, the percentage (persubscriber or collectively) of historically recorded content thatactually gets played back, and the like. As another example, theestimating may be based upon programming or viewing statistics for themedia content file itself In this regard, the RS-DVR system could beprovided with access to ratings information, recording data for othertime zones, or other information that is specific to the particularmedia content file.

The process 580 may continue by storing a plurality of recorded versionsof the media content file in the storage architecture without assigningany of the recorded versions to any of the subscribers at the time ofstoring (task 586). Notably, at least the predicted number (obtainedfrom the estimation of task 584) of unassigned recorded versions arestored and maintained in a pool of unassigned files. The RS-DVR systemmaintains this pool of unassigned recorded versions of the media contentfile until they are erased, where typically the erase decision is madeas a function of how old the media content is. It also may be that overtime some of the media content files in the pool are erased early due tominimal demand from subscribers. This example assumes that the RS-DVRsystem eventually receives a request for playback of the media contentfile, where the request originates from one of the supported subscribersystems or from another system or device that is being operated by asubscriber (the “YES” branch of query task 588).

In response to receiving the playback request, the RS-DVR system maydetermine whether any unassigned recorded versions of the media contentfile remain in the pool (query task 590). If not, then the RS-DVR systemtakes appropriate action. For example, the RS-DVR system may generateand send a message, a notification, or a status code to the requestingsubscriber system to indicate that the requested media content file isunavailable (task 592). Although this scenario is unlikely if theestimation of task 584 is accurate, the process 580 should contemplatethis situation and respond accordingly. If at least one unassignedversion of the requested media content file is available in the pool,the RS-DVR system assigns one of the unassigned recorded versions of themedia content file to the requesting subscriber, which results in anassigned recorded version (task 594). In certain embodiments, task 594exclusively assigns one of the unassigned recorded versions of the mediacontent to the requesting subscriber (and/or to the requestingsubscriber system), such that no other subscribers can access thatparticular version. Late assignment of the recorded content in thismanner results in the removal of an unassigned recorded version from thepool, or in the conversion of an unassigned recorded version in the poolinto an assigned recorded version. The RS-DVR system can then providethe assigned recorded version of the media content file to therequesting subscriber system for presentation or playback (task 596).

The late assignment technique described above still requires the user toinitiate the recording requests. To maintain consistency with legacy DVRsystems and copyright law precedence, the late assignment technique canbe performed in a transparent manner while still allowing end users tobelieve that they are actually controlling and initiating the recordingfunction. For example, activation of the “record” button on asubscriber's remote control is still required prior to the actualtransmission of the program, like it has to happen with a DVR. Adifference is that the user is not assigned to a specific copy of theprogram until the activation of the “play” button.

The above example assumes that the file assignment occurs at the time ofplayback. Alternatively, the RS-DVR system could be configured toconvert one of the unassigned recorded versions of the media contentfile into an assigned recorded version for a particular subscriber, eventhough playback is not immediately scheduled. In other words, assignmentof the media content file could be performed in response to any requestfor the media content file (e.g., a request from a subscriber system toview a list of recorded content), whether or not immediate playback isalso requested.

Storing Multiple Bitrate Versions Of Media Content In A Single File

Referring again to FIGS. 3-7, an adaptive rate RS-DVR system is capableof recording and saving multiple bitrate versions of each media contentfile in the form of multiple sets of encoded media segments. For oneexemplary embodiment, ten different bitrates are supported.Consequently, for such an embodiment the storage architecture 310 (FIG.3) maintains ten different sets of encoded media segments for each mediacontent file. Moreover, multiple instantiations of the ten differentsets may need to be maintained to comply with certain per-subscriberstorage requirements.

In accordance with an exemplary data storage and file system scheme, theRS-DVR system 300 records the different encoded bitrate versions of amedia content file in one logical file. The single logical file can bepartitioned for storage in a distributed manner across a plurality ofdifferent memory storage devices of the storage architecture 310. Thisfile management scheme can be accomplished by ensuring that the datarepresenting encoded media segments for any particular bitrate iscontiguous on a single memory storage device within the logical filestructure. The logical file structure may also be arranged such thatother video (media) segments of the logical file are stored on differentmemory storage devices.

In certain scenarios, the single logical file is partitioned such thatdata representing encoded media segments for different bitrates arestored on different memory storage devices. In other situations, a givenmemory storage device could be used to store encoded media segmentscorresponding to different bitrates, even though the stored mediasegments form part of the same logical file. The beginning of datarepresenting encoded media segments for the different bitrates islocated at known or specified offsets (e.g., predefined increments ofstorage space) to enable the file system module 306 to arrange, manage,and retrieve the encoded media segments for any particular bitrate in anefficient and effective manner, even though the encoded media segmentsfor a given bitrate might be stored on different memory storage devices.The offsets may be any predefined amount of storage space, e.g., 100 MBincrements. The offsets may, but need not, correspond to allocationunits for the memory storage devices. In practice, the offsets can beused to indicate the locations of nulls and/or the locations ofcontiguous data representing media segments encoded at a particularbitrate.

In practice, the RS-DVR system may utilize sparse file techniques andtechnology to enable the file system module 306 to store the multiplebitrate encoded media segments for a given media content file togetheras one logical file. To this end, the file system module 306 canallocate the different non-contiguous sections of the logical file ontodifferent memory storage devices. Storing different bitrates ondifferent memory storage devices in this manner is useful in dealingwith storage device failures or slow or excessively busy storagedevices. This file management and storage scheme also improves playbackperformance and reliability by locating specific bitrate segmentscontiguously within a single file structure and on the hard disk drives,which in turn facilitates read ahead and increasing disk efficiencies.

Referring again to FIG. 8, the RS-DVR system 300 stores encoded mediasegments for a given media content file as needed (task 506). In certainembodiments, task 506 is performed such that the encoded media segmentsare stored as a single logical file across a plurality of differentmemory storage devices of the storage architecture 310. During playbackof a particular media content file at a requested bitrate, the filesystem module 306 cooperates with the storage architecture 310 to accessand retrieve the appropriate encoded media segments. In this regard, thefile system module 306 can locate the corresponding logical file for therequested media content file (and for the requesting subscriber system),and then access or retrieve the appropriate media segments by consultinga table or metadata that indicates the offset location(s) for thedesired bitrate.

Simplified File Storage And Management

An RS-DVR system as described here could use a very simple storagemechanism for managing disk storage in storing per subscriber adaptiverate video content. In an exemplary embodiment, an index table (or anysuitable data arrangement) is kept in memory (and on disk) that mapseach disk block containing video to the subscriber, specific content,bitrate, and time offset within the content. The index table (whichfunctions similarly to a file system directory) can be only looselysynchronized with the actual content on the disk, because the storagemanager will validate the content when it is read from disk.

Referring again to FIG. 3, each of the memory storage devices (e.g.,hard disks) used for the storage architecture 310 of the RS-DVR system300 is divided into or otherwise defined as a plurality of allocationunits configured to store the encoded media segments. In preferredimplementations, all of the allocation units throughout the storagearchitecture 310 have the same predefined size, e.g., 2 MB or whateverarbitrary increment is desired. At least some of the allocations unitson any given hard disk will contain stored media segments—suchallocation units are referred to herein as “media segment containing”allocation units.

For the exemplary embodiment described here, each hard disk thatincludes at least one media segment containing allocation unit will alsohave a respective index table stored thereon. The index table includesentries for the media segment containing allocation units. Accordingly,if a particular hard disk includes some allocation units that do notstore any media segments, then the index table for that particular harddisk need not include entries for each and every allocation unit. Inpreferred deployments, the index table is used to store descriptivedata, metadata, or information that characterizes one or more encodedmedia segments stored in the media segment containing allocation units.

FIG. 12 depicts an exemplary index table 600 for maintaining descriptivedata related to encoded media segments. As mentioned above, at least oneindex table 600 may be stored on each hard disk that contains mediasegments. Accordingly, the size of the index table 600 is a function ofthe overall size of the hard disk. The index table 600 may be organizedsuch that it includes descriptive data for each media segment containingallocation unit 602. For example, the descriptive data may include,without limitation: a user identifier 604 corresponding to a subscribersystem or a subscriber; a content identifier 606 corresponding to theparticular media content file and to the encoded media segment(s) storedin the respective allocation unit; a bitrate identifier 608 thatindicates the bitrate corresponding to the encoded media segment(s)stored in the respective allocation unit; and a time index 610 for theencoded media segment(s) stored in the respective allocation unit. Itshould be appreciated that one allocation unit could be used to storeone or more “whole” media segments, one or more “partial” mediasegments, or any combination thereof. For example, a single allocationunit might be used to store only one encoded media segment, a pluralityof media segments, one complete media segment and a portion of a secondmedia segment, a portion of one media segment and a portion of anothermedia segment, etc. Accordingly, the actual content of an allocationunit entry in the index table may describe more than one encoded mediasegment if needed.

The RS-DVR system 300 (see FIG. 3) can generate, maintain, and updatethe index tables as needed to reflect ongoing changes to the recordedcontent stored on the memory storage devices. In preferred embodimentsthe index table 600 is written at the beginning of the memory storagedevice to facilitate immediate reading of the index table 600 when thememory storage device is mounted. Notably, any given index tableprovides a simple self-descriptive summary of the video content storedon its respective memory storage device. The file system module 306 canread and search the various index tables as needed to locate or identifyencoded media segments stored in the storage architecture 310.Accordingly, the file system module 306 may consult the index tables toaccess and retrieve requested media content files for playback.

As mentioned above, each index table describes the media content storedon the respective hard disk, and each index table may be written/updatedfrequently to continuously track the ongoing changes to the contentstored on the hard disk. For example, each index table could be writtenonce every thirty seconds. If a hard disk fails, then its correspondingdirectory as monitored by the file system module might be out ofsynchronization with what is actually present on the hard disk. TheRS-DVR system 300 employs a consistency check scheme to reduce thenegative consequences of such hard disk failures.

In accordance with the exemplary embodiment described here, eachallocation unit that includes a stored media segment includes aconsistency check field that contains at least some of the descriptivedata found in the index table for that particular hard disk. Morespecifically, the consistency check field for any given allocation unitcontains the descriptive data that characterizes the encoded mediasegments stored in that particular allocation unit. In other words,under normal operating conditions all of the consistency check fields ona hard disk will collectively include the same information thatpopulates the index table.

FIG. 13 is a diagram that depicts an exemplary embodiment of anallocation unit 620 having two consistency check fields 622, 624. Theallocation unit 620 includes a first instantiation of the consistencycheck field 622 located at a beginning section of the allocation unit620, along with a second instantiation of the consistency check field624 located at an ending section of the allocation unit 620. Duringoperation of the RS-DVR system 300, the file system module 306 can readone or both of the consistency check fields 622, 624 and compare thedata contained therein to the corresponding entry in the index table 600for that particular allocation unit 620. If the descriptive datamatches, then the file system module 306 assumes that the hard disk isoperating as expected and that the content of the allocation unit 620 issynchronized with that specified in the index table 600. If, however,the consistency check data is different than the index table data, thenthe RS-DVR system 300 can take appropriate action. For example, theRS-DVR system 300 may generate and send an appropriate notification ormessage to the subscriber system such that the subscriber system canrequest a different bitrate that is supported by properly operating harddisks. The two consistency check fields 622, 624 are located at thebeginning and end of the allocation unit 620 so that at least one of theconsistency check fields 622, 624 remains intact in the event of anerror or failure that occurs while writing video content to theallocation unit 620.

Disk Management Techniques

As described above with reference to FIGS. 3-8, each recording of amedia content file includes different encoded bitrate versions of thesame video, which allows the adaptive rate RS-DVR system to selectbetween different bitrates in real time during playback. In certainembodiments, the RS-DVR system records the different encoded bitrateversions of the same media content file on different hard disk drives.In practice, the media segment data itself may be divided at diskallocation unit boundaries and each allocation unit may be placed on adifferent hard disk drive, provided that no other video (of a differentbitrate within that time span for that subscriber is also on that samedisk). In the event of a disk drive failure, the RS-DVR system canaccess a different bitrate version that is on a hard disk drive that hasnot failed. Similarly, in the event that a hard disk drive is either toobusy or too slow to retrieve requested media content while maintainingreal-time delivery to the requesting subscriber system, the RS-DVRsystem can access and provide a different bitrate version that is on adisk drive that is not busy or too slow.

Referring again to FIG. 8, the encoded media segments (at differentbitrates) for a recorded media content file are stored in the storagearchitecture of the RS-DVR system during task 506. In accordance withcertain exemplary embodiments, the encoded media segments may includesets that correspond to the different supported bitrates. In thisregard, FIG. 14 is a diagram that depicts encoded media segments for amedia content file. For simplicity, FIG. 14 depicts three sets of mediasegments corresponding to three different bitrates: a low bitrate set ofmedia segments 702; an intermediate bitrate set of media segments 704;and a high bitrate set of media segments 706. Each media segment has arespective time range relative to the media content file. In otherwords, each media segment represents a relatively short time period ofthe overall media content file; each media segment corresponds to apartial period of playback time of the media content file. Although anyindividual media segment could have any designated time range, forconsistency with the examples described previously, each media segmentdepicted in FIG. 14 has a two second time range associated therewith.Thus, the leftmost media segment in each set has a time index of 00:00,the next media segment in each set has a time index of 00:02, and so on.Although FIG. 14 only shows five consecutive media segments in each set,it should be appreciated that the actual number of media segments forany given media content file will be dictated by the overall runtime ofthe video.

Storing of the encoded media segments of a media content file ispreferably performed in accordance with a distribution scheme to ensurethat encoded media segments having different bitrates and overlappingtime ranges are not stored on any common memory storage device. Thus,the RS-DVR system is configured and operated to prevent storage of anyencoded media segment together with another encoded media segment havingan overlapping partial period of playback time. One way to implementthis distribution scheme is to have each set of media segments 702, 704,706 stored on a different memory storage device. Another way toimplement this distribution scheme is to ensure that any given memorystorage device only contains one media segment having a particular timeindex (or time range). Accordingly, this distribution scheme may beinfluenced by a number of factors such as the different bitratesassigned to the media segments, the time ranges of the media segments,the time indices of the media segments, the identity of the mediacontent file, and the like.

Referring to FIG. 14, the media segments might be stored in adistributed manner as follows. Assume that the RS-DVR system includestwenty six hard disks identified by the letters of the alphabet. If themedia segment 702 a (which corresponds to the time index 00:00 for thefirst set of media segments 702) is stored on hard disk “A” then themedia segment 704 a and the media segment 706 a must be stored on twodifferent hard disks other than hard disk “A”. In other words, the mediasegments 702 a, 704 a, 706 a are distributed across three physicallydistinct and different hard disks. In contrast, the media segment 704 b(which corresponds to the time index 00:02 for the second set of mediasegments 704) could be stored on hard disk “A” because the time rangesof the media segment 702 a and the media segment 704 b do not overlap. Apractical deployment of the RS-DVR system might use hundreds of distincthard disk drives, which makes it easy to store media segments in adistributed manner with little to no conflicts.

Storage of the media segments in accordance with a distributed schemeenables the RS-DVR system to quickly and effectively respond to harddisk failures, hard disk errors, and otherwise unsatisfactory hard diskperformance. For example, in response to receiving a request forplayback of a media content file (see query task 508 of the process 500depicted in FIG. 8), the RS-DVR system can determine whether the memorystorage devices can maintain real-time delivery of the encoded mediasegments having the requested bitrate. This determination could beperformed by the file system module 306 and/or the processing logicmodule 302 (see FIG. 3) while monitoring the performance of the storagearchitecture 310. If the RS-DVR system determines that performance of amemory storage device is unsatisfactory, then the RS-DVR system can takeappropriate action. For example, the RS-DVR system could generate anHTTP status code, generate and send a message intended for therequesting subscriber system, or take other action as described abovewith reference to the process 520 illustrated in FIG. 9.

As used here, “unsatisfactory performance” for a memory storage devicecontemplates: a complete or temporary failure of a memory storagedevice; operation of a memory storage device below a threshold speedthat is required to maintain real-time delivery of the encoded mediasegments having the requested bitrate; operation of a memory storagedevice at a workload level that causes the device to be too busy tomaintain real-time delivery of the encoded media segments having therequested bitrate; or the like. Notably, the distributed storage schemeoutlined above allows the RS-DVR system to address unsatisfactory harddisk performance by temporarily bypassing that particular hard disk toaccess one or more good hard disks that maintain the same video content(having some media segments encoded at a bitrate other than therequested bitrate). In other words, distributing the media segmentsacross a plurality of distinct memory storage devices enables the RS-DVRsystem to “sacrifice” one (or more) hard disks while still being able todeliver the requested media content file to the requesting subscribersystem.

While at least one exemplary embodiment has been presented in theforegoing detailed description, it should be appreciated that a vastnumber of variations exist. It should also be appreciated that theexemplary embodiment or embodiments described herein are not intended tolimit the scope, applicability, or configuration of the claimed subjectmatter in any way. Rather, the foregoing detailed description willprovide those skilled in the art with a convenient road map forimplementing the described embodiment or embodiments. It should beunderstood that various changes can be made in the function andarrangement of elements without departing from the scope defined by theclaims, which includes known equivalents and foreseeable equivalents atthe time of filing this patent application.

What is claimed is:
 1. A remote storage digital video recorder (RS-DVR)system comprising: a network interface to communicate data between theRS-DVR system and a subscriber system via a network; a file systemmodule coupled to the network interface; an ingest agent coupled to thefile system module to receive encoded media segments that represent amedia content file encoded at a plurality of different bitrates, whereinthe encoded media segments include a respective set of encoded mediasegments corresponding to each of the plurality of different bitrates,and wherein each of the encoded media segments has a time range relativeto the media content file; and a plurality of memory storage devicescoupled to the file system to store the encoded media segments inaccordance with a distribution scheme influenced by the plurality ofdifferent bitrates and time ranges of the encoded media segments.
 2. TheRS-DVR system of claim 1, wherein: in accordance with the distributionscheme, each of the plurality of memory storage devices stores theencoded media segments such that the time ranges do not overlap for theplurality of different bitrates.
 3. The RS-DVR system of claim 1,wherein: in accordance with the distribution scheme, encoded mediasegments having different bitrates and overlapping time ranges are notstored on a common one of the plurality of memory storage devices. 4.The RS-DVR system of claim 1, wherein: in accordance with thedistribution scheme, the encoded media segments for each of theplurality of different bitrates are stored in a different one of theplurality of memory storage devices.
 5. The RS-DVR system of claim 1,wherein: the network interface receives a request for playback of themedia content file, the request identifying the media content file and arequested bitrate for the media content file; the file system modulemonitors performance of the plurality of memory storage devices; andwhen the file system module determines that performance of one of theplurality of memory storage devices storing the encoded media segmentsfor the requested bitrate is unsatisfactory, the RS-DVR system generatesa message intended for the subscriber system, the message instructingthe subscriber system to request a different bitrate for the mediacontent file.
 6. The RS-DVR system of claim 1, wherein: the networkinterface receives a request for playback of the media content file, therequest identifying the media content file and a requested bitrate forthe media content file; the file system module monitors performance ofthe plurality of memory storage devices; and when the file system moduledetermines that performance of one of the plurality of memory storagedevice storing the encoded media segments for the requested bitrate isunsatisfactory, the RS-DVR system generates a message intended for thesubscriber system, the message indicating that the requested bitrate forthe media content file is unavailable.
 7. The RS-DVR system of claim 1,wherein: the network interface receives a request for playback of themedia content file, the request identifying the media content file and arequested bitrate for the media content file; the file system modulemonitors performance of the plurality of memory storage devices; andwhen the file system module determines that performance of one of theplurality of memory storage device storing the encoded media segmentsfor the requested bitrate is unsatisfactory, the RS-DVR system selects adifferent bitrate for the media content file.
 8. A method of operating aremote storage digital video recorder (RS-DVR) system that supports asubscriber system via data communication over a network, the methodcomprising: receiving, at the RS-DVR system, encoded media segments thatrepresent a media content file encoded at a plurality of differentbitrates, wherein the encoded media segments include a respective set ofencoded media segments corresponding to each of the plurality ofdifferent bitrates, and wherein each of the encoded media segments has atime range relative to the media content file; storing the encoded mediasegments in a plurality of memory storage devices of the RS-DVR system,wherein the storing is performed in accordance with a distributionscheme to ensure that encoded media segments having different bitratesand overlapping time ranges are not stored on a common one of theplurality of memory storage devices; after storing the encoded mediasegments, receiving, at the RS-DVR system, a request for playback of themedia content file, the request identifying a requested bitrate for themedia content file; determining, at the RS-DVR system, whether theplurality of memory storage devices can maintain real-time delivery ofencoded media segments having the requested bitrate; and when the RS-DVRsystem determines that one of the plurality of memory storage devicescannot maintain real-time delivery of encoded media segments having therequested bitrate, generating, at the RS-DVR system, a message intendedfor the subscriber system, wherein the message instructs the subscribersystem to request a different bitrate for the media content file.
 9. Themethod of claim 8, wherein: the RS-DVR system supports a plurality ofdifferent subscriber systems via data communication over the network;and the RS-DVR system receives encoded media segments that represent aplurality of different media content files encoded at a plurality ofdifferent bitrates.
 10. The method of claim 8, wherein the determiningstep determines when one of the plurality of memory storage devices hasfailed.
 11. The method of claim 8, wherein the determining stepdetermines when one of the plurality of memory storage devices isoperating below a threshold speed required to maintain real-timedelivery of the encoded media segments having the requested bitrate. 12.The method of claim 8, wherein the determining step determines when oneof the plurality of memory storage devices is too busy to maintainreal-time delivery of the encoded media segments having the requestedbitrate.
 13. A method of operating a remote storage digital videorecorder (RS-DVR) system that supports at least one subscriber systemvia data communication over a network, the at least one subscribersystem providing media content to at least one subscriber, the methodcomprising: receiving, at the RS-DVR system, a first set of encodedmedia segments that represent a media content file encoded at a firstbitrate, and a second set of encoded media segments that represent themedia content file encoded at a second bitrate, wherein each encodedmedia segment in the first set of encoded media segments corresponds toa respective partial period of playback time of the media content file,and wherein each encoded media segment in the second set of encodedmedia segments corresponds to a respective partial period of playbacktime of the media content file; receiving, at the RS-DVR system, aninstruction to record the media content file on behalf of a subscriber;and in response to receiving the instruction, storing the first set ofencoded media segments and the second set of encoded media segments in aplurality of physically distinct memory storage devices in a distributedmanner to prevent storage of any member of the first set of encodedmedia segments together with any member of the second set of encodedmedia segments that has an overlapping partial period of playback timeof the media content file.
 14. The method of claim 13, furthercomprising: after storing the first and second sets of encoded mediasegments, receiving, at the RS-DVR system, a request for playback of themedia content file, the request identifying a requested bitrate for themedia content file; determining, at the RS-DVR system, whether theplurality of memory storage devices can maintain real-time delivery ofencoded media segments having the requested bitrate; and when the RS-DVRsystem determines that one of the plurality of memory storage devicescannot maintain real-time delivery of encoded media segments having therequested bitrate, generating, at the RS-DVR system, a message intendedfor the subscriber system.
 15. The method of claim 14, wherein themessage instructs the subscriber system to request a different bitratefor the media content file.
 16. The method of claim 14, wherein themessage informs the subscriber system that the requested bitrate isunavailable.
 17. The method of claim 14, wherein the determining stepdetermines when one of the plurality of memory storage devices hasfailed.
 18. The method of claim 14, wherein the determining stepdetermines when one of the plurality of memory storage devices isoperating below a threshold speed required to maintain real-timedelivery of the encoded media segments having the requested bitrate. 19.The method of claim 14, wherein the determining step determines when oneof the plurality of memory storage devices is too busy to maintainreal-time delivery of the encoded media segments having the requestedbitrate.
 20. The method of claim 13, further comprising: after storingthe first and second sets of encoded media segments, receiving, at theRS-DVR system, a request for playback of the media content file, therequest identifying a requested bitrate for the media content file;determining, at the RS-DVR system, whether the plurality of memorystorage devices can maintain real-time delivery of encoded mediasegments having the requested bitrate; and when the RS-DVR systemdetermines that one of the plurality of memory storage devices cannotmaintain real-time delivery of encoded media segments having therequested bitrate, providing encoded media segments having a bitrateother than the requested bitrate.